FIG. 1(A) shows an example of a semiconductor device used for conventional bare chip (flip chip) mounting. A semiconductor device 1 shown in that figure is generally made up of a semiconductor element (semiconductor chip) 2, and a large number of protruding electrodes (bumps) 4.
The protruding electrodes 4 serving as external connection terminals are arranged, for example, in a matrix formation, on a lower surface of the semiconductor element 2. The protruding electrodes 4 are formed of a soft metal such as solder, and are thus liable to take scratches. Thus, it is difficult to handle and test the protruding electrodes. Similarly, the semiconductor element 2 is in a bare chip formation and is thus liable to take scratches. Thus, it is also difficult to handle and test the semiconductor element 2 as in the case of the protruding electrodes 4.
As shown in FIG. 1(B), the above semiconductor device 1 is mounted on a mount board 5 (for example, a printed wiring board) as follows. First, the protruding electrodes 4 of the semiconductor device 1 are bonded to electrodes 5a formed on the mount board 5. Subsequently, as shown in FIG. 1(C), a so-called under fill resin 6 (indicated by a pear-skin illustration) is provided between the semiconductor element 2 and the mount board 5.
The under fill resin 6 is formed so that a space 7 (approximately equal to the height of the protruding electrodes 4) formed between the semiconductor element 2 and the mount board 5 is filled with a resin having a flowability.
The under fill resin 6 thus formed is provided to prevent occurrence of a break of a bonded portion between the protruding electrodes 4 and the electrodes 5a of the mount board 5 or a bonded portion between the protruding electrodes 4 and the electrodes of the semiconductor element 2 due to stress resulting from a difference in thermal expansion between the semiconductor element 2 and the mount board 5 and stress generated when heat applied at the time of mounting is removed.
As described above, the under fill resin 6 is effective because it functions to prevent occurrence of a break of the bonded portion between the protruding electrodes 4 and the mount board 5 (particularly, a break of the bonded portion between the electrodes of the mount board 5 and the protruding electrodes 4). However, a troublesome filling work is required because the under fill resin 6 is provided in the narrow space 7 between the semiconductor element 2 and the mount board 5. Further, it is difficult to uniformly provide the under fill resin 6 in the whole space 7. Hence, the efficiency in fabrication of the semiconductor device is reduced. Further, the bonded portion between the protruding electrodes 4 and the electrodes 5a or the bonded portion between the protruding electrodes 4 and the semiconductor element 2 may be damaged though the under fill resin 6 is provided. Hence, the reliability in mounting is degraded.
A Further, the above semiconductor device 1 is mechanically weak and a low reliability because the semiconductor element 2 is mounted on the mount board 5 in a state in which the semiconductor element 2 is exposed.
Furthermore, the protruding electrodes 4 are formed directly on electrode pads formed on the lower surface of the semiconductor element 2. Hence, the layout of the electrode pads is automatically equal to the layout of the protruding electrodes 4. That is, the semiconductor device 1 does not have degree of freedom in routing wiring lines within the inside thereof, and has a low degree of freedom in layout of the protruding electrodes 4 serving as the external connection terminals.
The present invention is made taking into account the above disadvantages, and has an object to provide a method and mold for fabricating a semiconductor device and a semiconductor device, and a semiconductor device having an improved efficiency in fabrication and improved reliability.
The present invention has another object to provide a semiconductor device, a method for fabricating the same and a method for mounting the semiconductor device having an increased degree of freedom in layout of terminals and improved reliability.